This invention springs from the problems and shortcomings of existing locks. It operates with a combination, because keys are troublesome; and it operates with a single knob, so it can be opened with one hand. Its combination uses detents so it can be operated by sound and feel and opened in the dark, and its single operating knob makes it tamperproof. It gives a potential intruder no clue about any combination setting and requires a complete combination sequence to be followed before the lock can be tried. It also offers a large number of combinational possibilities so that it is effectively secure against combination reading attempts. Finally, it combines all these features in a practical and economical lock that can be mass produced at low cost, made sturdy and reliable, and conveniently adjusted to any one of its many combinational possibilities.